New Cochlear Implant Recharges Wirelessly With No External Hardware

Cochlear implants electronically stimulate the auditory nerve, giving hundreds of thousands of patients hearing that would otherwise be deaf. Current versions of the device require a disk-shaped transmitter, an inch in diameter, be affixed to the skull. Researchers may have designed a sleeker implant.

"Researchers at MIT's Microsystems Technology Laboratory (MTL), together with physicians from Harvard Medical School and the Massachusetts Eye and Ear Infirmary (MEEI), have developed a new, low-power signal-processing chip that could lead to a cochlear implant that requires no external hardware. The implant would be wirelessly recharged and would run for about eight hours on each charge," according to a release announcing the findings.

The researchers will present their finds at the International Sold-State Circuits Conference later this week.

"The idea with this design is that you could use a phone, with an adaptor, to charge the cochlear implant, so you don't have to be plugged in," said Anantha Chandrakasan, the corresponding author on the paper. "Or you could imagine a smart pillow, so you charge overnight, and the next day, it just functions."

While current implants use an external microphone to capture sound, the new implants would use the "natural microphone of the middle ear," which is typically undamaged in cochlear-implant patients.

"The researchers' design exploits the mechanism of a different type of medical device, known as a middle-ear implant. Delicate bones in the middle ear, known as ossicles, convey the vibrations of the eardrum to the cochlea, the small, spiral chamber in the inner ear that converts acoustic signals to electrical. In patients with middle-ear implants, the cochlea is functional, but one of the ossicles - the stapes - doesn't vibrate with enough force to stimulate the auditory nerve. A middle-ear implant consists of a tiny sensor that detects the ossicles' vibrations and an actuator that helps drive the stapes accordingly," MIT said in its news release. 

The new device would use a similar sensor, but the signal would travel to a microchip implanted in the ear, where it would be converted to an electric signal and deliverd to the cochlea.

"It's very cool," said Lawrence Lustig, director of the Cochlear Implant Center at the University of California at San Francisco. "There's a much greater stigma of having a hearing loss than there is of having a visual loss. So people would be very keen on losing the externals for that reason alone. But then there's also the added functional benefit of not having to take it off when you're near water or worrying about components getting lost or broken or stolen. So there are some important practical considerations as well."